Development of mixing rules for predicting the viscosity of bitumen and its fractions blended with toluene

A comprehensive model is presented for predicting the liquid‐mixture viscosity of bitumen and its fractions diluted with toluene. The proposed model is based on the Walther two‐parameter viscosity‐temperature correlation and a simple viscosity mixing rule. New viscosity data at 22‐100°C are presented for 14 blends of Cold Lake bitumen and its fractions with toluene. All of these data are well correlated by the Walther correlation with AAD < 2%. The predictions from a recently proposed simple mixing formula for toluene‐bitumen blends viscosity are well within an order of magnitude of the data. The blend viscosity predictions are improved substantially by use of a temperature‐dependent viscous interaction parameter. For predicting the viscosity of toluene‐diluted whole bitumen, the bitumen is characterized both as a “black‐oil” and as a mixture of five fractions or pseudocomponents. The calculation procedure for the viscosity of toluene‐diluted bitumen is outlined and the two characterization approaches are evaluated.